The conventional image data processing equipment comprises a color RAM which holds a number of color information to be used, and an object data memory which holds object data which holds address information of the color RAM.
FIGS. 12A to 12C show memory maps of the object data memory and the color RAM of the conventional image data processing equipment. The maps comprise a bitmap of 8 successive pixels for respective colors A-H as shown in FIG. 12A, a color RAM which holds RGB data of the colors A-H (FIG. 12C), and an object data memory which holds address information (0-7) of the color RAM (FIG. 12B).
The color RAM of FIG. 12C is accessed based on addresses held by the object data memory of FIG. 12B to output color information of the object data held by the object data memory.
Such conventional image data processing equipment needs, as the object data memory, a large capacity memory having capacities for a number of pixels on the bitmaps. This hinders downsizing of the equipment and cost reduction. This is a problem.
An object of the present invention is to provide a data compressing method which can efficiently compress image data containing color data.
Another object of the present invention is to provide an image data memory which can efficiently compress image data containing color data and store the compressed image data.
A further another object of the present invention is to provide a compressed data expanding method and system which can quickly expand compressed data on a bitmap.